The present invention relates to a hard medicinal capsule shaped of a novel polymeric composition as well as to a method for shaping such a hard capsule formed of the polymeric composition.
As is well known, the most widely used material of hard medicinal capsules in the prior art is gelatin and a hard medicinal capsule of gelatin is prepared usually in a process in which a mandrel pin is dipped in a bath of an aqueous solution of gelatin followed by withdrawing of the pin out of the solution and drying of the solution on the pin to form a crust of gelatin and the mandrel pin is pulled away from the gelatin crust which is then trimmed into a finished form.
Gelatin-made hard medicinal capsules prepared in this manner, however, have several problems and disadvantages, for example, that gelatin is a proteinaceous material with reactivity so that certain medicament ingredients contained in a gelatin capsule may interact with gelatin and be denatured, that a gelatin capsule prolongedly kept under an extremely low humidity may become brittle and sometimes is broken in handling while, when a gelatin-made medicinal capsule is kept under a highly humid condition, the medicament ingredient may sometimes be denatured due to the increased moisture inside the capsule and that gelatin is liable to the attack of microorganisms so that the quality of a gelatin-made hard capsule is unavoidably degraded in the lapse of time.
With an object to overcome the above mentioned problems and disadvantages of gelatin-made hard medicinal capsules, proposals and attempts have been made to shape a hard medicinal capsule of a material other than gelatin. For example, cellulose ethers with alkyl or hydroxyalkyl groups as the substituents on the cellulose molecules are proposed in the form of an aqueous or organic solution as a substitute of the aqueous solution of gelatin for the preparation of hard medicinal capsules. These cellulose derivatives, however, are not quite satisfactory as a material of medicinal capsules due to the relatively large permeability of the capsule walls made thereof to oxygen and moisture resulting in the denaturation of the medicament ingredients contained in the capsule. Other materials hitherto proposed as a base of hard medicinal capsules include starch, .alpha.-starch, hydroxyalkyl starch, sodium alginate, sodium salt of a copolymer of gelatin and acrylic acid and the like although hard capsules made of these materials are hardly applicable to practical use due to the low mechanical strength of the capsule and possible reactivity of the capsule walls with the medicament ingredients as a consequence of the ionic nature of the material.